Journal ArticleDOI
Contrast in complex images.
TLDR
A definition of local band-limited contrast in images is proposed that assigns a contrast value to every point in the image as a function of the spatial frequency band and is helpful in understanding the effects of image-processing algorithms on the perceived contrast.Abstract:
The physical contrast of simple images such as sinusoidal gratings or a single patch of light on a uniform background is well defined and agrees with the perceived contrast, but this is not so for complex images. Most definitions assign a single contrast value to the whole image, but perceived contrast may vary greatly across the image. Human contrast sensitivity is a function of spatial frequency; therefore the spatial frequency content of an image should be considered in the definition of contrast. In this paper a definition of local band-limited contrast in images is proposed that assigns a contrast value to every point in the image as a function of the spatial frequency band. For each frequency band, the contrast is defined as the ratio of the bandpass-filtered image at the frequency to the low-pass image filtered to an octave below the same frequency (local luminance mean). This definition raises important implications regarding the perception of contrast in complex images and is helpful in understanding the effects of image-processing algorithms on the perceived contrast. A pyramidal image-contrast structure based on this definition is useful in simulating nonlinear, threshold characteristics of spatial vision in both normal observers and the visually impaired.read more
Citations
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Proceedings ArticleDOI
Photographic tone reproduction for digital images
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Journal ArticleDOI
Information Content Weighting for Perceptual Image Quality Assessment
Zhou Wang,Qiang Li +1 more
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Book
Modern image quality assessment
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TL;DR: This book is about objective image quality assessment to provide computational models that can automatically predict perceptual image quality and to provide new directions for future research by introducing recent models and paradigms that significantly differ from those used in the past.
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Perceptual visual quality metrics: A survey
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Image quality assessment based on a degradation model
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References
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Journal ArticleDOI
Merging thermal and visual images by a contrast pyramid
TL;DR: A hierarchical image merging scheme based on a multiresolution contrast decomposition (the ratio of a low-pass pyramid) is introduced, which shows that the fused images present a more detailed representation of the depicted scene.
Journal ArticleDOI
The cortex transform: rapid computation of simulated neural images
TL;DR: A transform which maps an image into a set of images that vary in resolution and orientation, each pixel in the output may be regarded as the simulated response of a neuron in human visual cortex is described.
Journal ArticleDOI
Psychophysics of reading--II. Low vision.
TL;DR: Estimates of the best reading performance to be expected from low-vision observers with characteristic forms of vision loss, and the stimulus parameters necessary for optimal performance, are provided.
Journal ArticleDOI
What does the eye see best
TL;DR: It is shown here that, within the range that the authors have been able to test, there is a particular spatiotemporal pattern of light that is detected better than any other, and it is proposed that this is the weighting function of the most efficient human contrast detector.
Journal ArticleDOI
Visual Contrast Sensitivity
TL;DR: In this article, the authors measured the contrast sensitivity of the human eye with sinusoidal grating targets of various spatial frequencies and found that the shape of the contrast-sensitivity function and its absolute values show good agreement among normal subjects, but the most interesting properties of this function cannot be attributed to the optics of the eye, but must be understood in terms of the image processing activities of the visual pathways.